Chtholon is produced by the chtholon extractor structure, which will be built automatically on ramjet yards and ramjet component autofacs if they are not provided chtolon through trade with a dedicated chtolon extractor world or trade hub. Chtholon extraction consumes two units of aetherium for every unit of chtholon produced. Worlds with chtholon deposits always have aetherium deposits as well, so a dedicated chtholon extractor world does not need to be supplied with aetherium throuigh trade (although it will produce much more chtholon if it is). Although chtholon is resource-intensive to produce, advanced ramjets are the most powerful ships in the game on a unit-for-unit basis.
Chtholon is derived from the word chthonic: 'relating to things that are beneath the ground or in the underworld'. The word also carries intimations of concealment, death, and great age. Appropriately, it is most abundant on chthonic and hadean worlds; hadean is derived from Hades: 'the ancient Greek god of death and the underworld'.